Persistence of an alternate chromatin structure at silenced loci in the absence of silencers
Persistence of an alternate chromatin structure at silenced loci in the absence of silencers
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DOI：
10.1073/pnas.95.10.5521
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发表时间：
1998-05-12
影响因子：
11.1
通讯作者：
Gartenberg, MR
中科院分区：
文献类型：
--
作者：
Cheng, TH;Li, YC;Gartenberg, MR
在酿酒酵母中，位于端粒或沉默的HML和HMR交配型基因座附近的基因被异染色质样结构转录抑制。我们通过体内重组产生了非复制DNA环，以研究染色体背景对转录抑制的作用。具体地，在HMR处的重组用于产生缺少E和I沉默子的环。在这些环中观察到DNA超螺旋水平的改变，但在去阻遏位点的可比环中没有观察到。我们的研究结果表明，一个压抑的染色质结构持续在染色体外的环境中，立即删除顺式作用的控制元件。染色质足迹和DNA序列依赖性的检查显示，核小体数量的变化可以解释拓扑结构的变化。细胞继续生长后，超螺旋的差异消失，转录能力恢复。这些结果表明，沉默剂需要持续持久的抑制性染色质结构，即使在没有DNA复制。
In Saccharomyces cerevisiae, genes placed near telomeres or the silent HML and HMR mating-type loci are transcriptionally repressed by a heterochromatin-like structure. We have generated nonreplicating DNA rings by recombination in vivo to examine the role of chromosomal context on transcriptional repression. Specifically, recombination at HMR was used to produce rings that lacked the E and I silencers. An altered level of DNA supercoiling was observed in these rings but not in comparable rings from derepressed loci. Our results indicate that a repressive chromatin structure persists in an extrachromosomal environment immediately following removal of the cis-acting control elements. Examination of both chromatin footprints and DNA sequence dependence revealed that changes in nucleosome number could account for the topology shifts. Upon continued cell growth, the differences in supercoiling were lost and transcriptional competence was restored. These results show that silencers are required for sustained persistence of repressive chromatin structure, even in the absence of DNA replication.